1) Field of the Invention
The invention herein relates to a reflective-type liquid crystal projection system.
2) Description of the Prior Art
According to the principles utilized during optical diffraction and focusing, the conventional liquid crystal projection television systems can be generally classified as transparent (TFT) or reflection (LCD) types. Since the transparent-type liquid crystal projection television systems were developed earlier, the components utilized in the said systems are more mature. However, with respect to the liquid crystal panels, since the resolution and clarity of reflective-type liquid crystal display panels is superior and, furthermore, lower in price, more and more liquid crystal projection television manufacturers plan to use reflective-type liquid crystal display panels designs.
Referring to FIG. 1, a conventional transparent-type TFT liquid crystal projection television system consists of a projection bulb 10. The light generated by the said projection bulb 10 is passing through a filter lens group 11 and then sequentially passing through a reflection mirror 130, a lens group 14, and a dichroic mirror 150 after being filtered, such that the said light is diffracted into two beams of different wavelengths. After the one beam of light is sequentially passing a reflection mirror 133 and a convergent lens 160, it is projected onto a red transparent-type liquid crystal display (R-TFT) panel 170. The other beam of light is directed towards another dichroic mirror 151 and further diffracted into two beams of light. The said two beams of light are then passing through reflection mirrors 131 and 132 as well as the convergent lens 161, 163, and 164, and are projected onto a green transparent-type liquid crystal display (G-TFT) panel 171 and a blue transparent-type liquid crystal display (B-TFT) panel 172 respectively. After diffraction, the said three beams of light travel through the red transparent-type liquid crystal display (R-TFT) panel 170, the green transparent-type liquid crystal display (G-TFT) panel 171, and the blue transparent-type liquid crystal display (B-TFT) panel 172, and let the red, green and blue images shown thereon be projected to a polarizing beam splitter (PRS) prism 18. The said polarizing beam splitter prism 18 merged these images into a single image, which is then penetrating a projection lens 190 and is projected onto a television screen 191 for viewing. Therefore, in a transparent-type TFT liquid crystal display projection television system, two dichroic mirrors 150 and 151 are utilized to diffract the light generated by the projection bulb 10 into three light beams of different wavelengths, such that the image of the said light beams reaching the red transparent-type liquid crystal display (R-TFT) panel 170, the green transparent-type liquid crystal display (G-TFT) panel 171, and the blue transparent-type liquid crystal display (B-TFT) 172 are projected to a polarizing beam splitter prism 18 and merged into a single image by the said polarizing beam splitter prism 18.
Referring to FIG. 2, a conventional reflective-type LCD projection television system also consists of a projection bulb 20. The light generated by the said projection bulb 20 is passing through a filter lens group 21 and then passing through a dichroic mirror 220 after being filtered, where the said light is diffracted into two light beams of different wavelengths. One beam thereof sequentially passes through a reflection mirror 230 and a convergent lens 240, and is projected to a first polarizing beam splitter prism 250. After passing the said prism 250, the beam of light is reflected to a red reflective-type liquid crystal display (R-LCD) panel 260. The other beam of light passes through the reflection mirrors 231 and 232 as well as another dichroic mirror 221 respectively, and is further diffracted into two beams of light. The said two beams of light then respectively pass through the convergent lens 241 and 242 and projected to a second and a third polarizing beam splitter prism 251 and 252. The said two prisms 251 and 252 respectively reflect them to a green reflective-type liquid crystal display (G-LCD) panel 261 and a blue reflective-type liquid crystal display (B-LCD) panel 262. After the said diffracted beams of light are projected onto the reflective-type liquid crystal display panels 260, 261 and 262, the red, green and blue images shown thereon are respectively reflected to a fourth polarizing beam splitter prism 27 through the said prisms 250, 251, and 252. The said fourth polarizing beam splitter prism 27 merges these images into a single image, which is then penetrating a projection lens 28 and is projected onto a television screen for viewing.
As described above, although the said reflective-type liquid crystal display panel has superior resolution and clarity and, furthermore, the advantage of lower price, since the overall system utilizes a larger quantity of optical components and, furthermore, the optical structure is more complex, its physical dimensions are larger and thus its overall production cost is higher.
In view of the foregoing situation, to improve upon the shortcomings of the said conventional reflective-type liquid crystal projection system, the inventor of the invention herein conducted extensive research and testing that culminated in the successful design of the reflective-type liquid crystal projection system of the invention. The said system consists of a dichroic mirror that diffracts the light beam generated by a light source module into two colored light beams of different wavelengths; and three polarizing light flux splitter prisms that are symmetrically disposed around the dichroic prism as well as two related converging lens groups, such that the three RGB color images shown on three reflective-type liquid crystal display panels are merged into a single image and then projected onto a television screen for viewing. As a result, the structural design of the present invention is simpler and, furthermore, the overall physical dimensions are smaller than the conventional reflective-type liquid crystal projection television system, thereby effectively reducing production, storage, and shipping costs.